Im having difficulties with this question?

The following context-free grammar, G, generates an algebraic language, where all variables are one letter, which is either x, y, or z. The start symbol of G is E.

1. E E + E
2. E E - E
3. E - E
4. E E _* E
5. E (E)
6. E x
7. E y
8. E z

Prove that G is ambiguous by writing two leftmost derivations for the string x + y + z. Which one of those would be considered "correct"?